The present invention has application within the environment of analog video extenders. In modern environments, one embodiment is incorporated into keyboard, video mouse (KVM) switches that connect multiple user workstations (such as keyboards, mice, monitors, etc.) with selected ones of multiple different servers. Analog KVM switches route video between the workstations and the servers in the analog domain and provide for high bandwidth real-time video and multimedia transmissions. One such analog KVM switch is the analog matrix switch (AMS) developed and sold by Avocent Corporation of Huntsville, Ala. An example analog switch architecture is shown in FIG. 1.
In FIG. 1, the system is made up of servers 10–15, computer interface pods (CIP) 16–21, analog matrix switches (AMS) 22–24, analog user pods (AUP) 31–35, and user workstations 36–40. Also shown in FIG. 1 are a hub 26 communicating with switch or router 27, communicating with corporate LAN 28, and communicating with a matrix system administrator (MSA) 29 operating on a computer 30. Also shown in FIG. 1 is a local computer 41 communicating with workstation 40 through CIP 41 and AUP 35.
The example in FIG. 1 is but one example embodiment of how the AMS system can be arranged into a distributed architecture, and many other architectures (both of simpler and more complex arrangement) will be understood to the artisan upon review of FIG. 1. Further, the example of FIG. 1 is described simply to give an example context into which the present invention may have application and in no way is intended to limit the broad aspects of the present invention.
The system in FIG. 1 provides command, control, and switching of KVM signals between servers 10–15 and workstations 36–40, as well as controlled by MSA application 29 of the system as a whole. The AMS system of FIG. 1 operates independently of software applications on the servers or workstations. In essence, the system is responsible for establishing connectivity paths between users at the workstations 36–40 and servers 10–15, switching and routing of KVM signals throughout the system, user authentication, and software upgrades at the unit end system level as directed by the MSA 29.
As background, the AMS 22–24 connects to servers 10–15 via CIPs 16–21. CIPs convert the native KVM connections to proprietary long distance signals and serves as the interface between an individual server and the KVM matrix system. The connections between CIP and the AMS units can be by industry standard UTPlus cabling, as are all other connections between the system elements.
On the workstation side, users are connected to the AMS 22–24 via AUPs 31–35. AUPs are a desktop design with a universal power supply and can provide peripheral support for a variety of different workstation types, such as PS/2, Sun, etc. As shown in FIG. 1, the AUP may be directly connected via UTPlus cable to one-to-four AMS or CIP modules. The AUPs can be in a mix and match configuration, such as AUP 34, which communicates with AMS 25 and CIP 21.
Because structure of the system employing the present invention is not a critical aspect of the present invention, the example of FIG. 1 is relevant only for its illustration of transmission of analog video signals between the component servers, CIPs, AMSs, AUPs, and the workstation.
In an example of FIG. 1, the AMS 22–25 connects to servers 10–15 via CIP 16–21 to convert KVM signals from native connectors and cabling to long line (long distance) communication protocols. The physical connection between the CIPs and the AMSs is via UTPlus cable. On the other end, the AMSs 22–24 connect to AUPs 31–35 also by UTPlus cable. The maximum distance between CIPs and AUPs is dictated by the degradation that occurs in the analog video signal over long distances. Distances between CIPs and AUPs of about 300 meters are difficult to obtain for high bandwidth, high quality video having present compensation schemes. The principle purpose of the AMS is to switch video (and data) between any of its inputs and outputs, thereby connecting selected workstations 36–40 with selected computers 10–15.
The analog user pod (AUP) is the main user console interface component of the AMS system. The AUP 31–35 provides KVM connectivity between the user console and either AMSs 22–25 or CIPs 16–21. Because a video degradation occurs in the cabling, the present invention relates to methods for correcting the video distortion caused by signal losses in the video transmission. In one example, such correction occurs in the AUP 31–35 and is carried out during each switch from a user to a server. The AUP also provides on-screen display menu-based technology to permit users to select new computers for connection via an on-screen menu. Each time the user employs the OSD menu to select a new computer, the video correction functions can be performed by the AUP to permit fully compensated video to be provided to the user shortly after the switch request is initiated.
On the other end, the computer interface pod (CIP) converts computer KVM signals into a format that can be transmitted down UTPlus cable to the AMS or AUP. All of the UTPlus cable described herein is usually four-pair unshielded, twisted pair cable that is rated category five or better. Other alternative cables are, of course, employable in a system that also employs the compensation systems of the present invention. Each CIP employs one KVM computer port, using native connectors for servers 10–15.
The matrix switch administrator (MSA) 29 is a client software on computer 30 that allows the administrator of the analog matrix system to easily configure, monitor and maintain the system from a remote computer 30 on an attached LAN 28 or connected via a cross-over cable. The MSA 29 allows the administrator to perform functions such as user settings, server settings, system monitoring, system administration, system logging, etc. The MSA 29 may also perform port status, event logging, trace routing, etc., via it's network port.
As previously described, in the system of FIG. 1, and other analog matrix switching systems, analog video is degraded as it travels along cables. The present invention compensates for video distortion on industry standard cabling (such as CAT5, CAT5e and CAT-6 (including gigaflex), and any other standard cabling) to provide high quality video up to 1,000 feet away from servers 10–15. The compensation is accomplished by three compensation features, used independently or in any combination. The first is automatic adaptive cable equalization in which the system automatically corrects for frequency dependent attenuation each time a valid KVM path is selected. The second is automatic adaptive cable de-skew compensation that automatically detects and corrects for inter-pair delay skew that is inherent in, for example, CAT5 style cables. The third is compensation obtained by reducing data link pair cross talk in CAT5 RJ45 connectors.